Thor's godforce has proven capable of defeating Galactus so he might be able to pull it off. The question that occurs to me is what sort of energy is manifested by the godforce and will it do one of the two things necessary. It has been stated that any of Galactus' heralds can make a star go nova. Thor is supposedly as powerful as the Silver Surfer even without the Odinpower.
To imply that Thor could possibly hope to defeat a cosmic entity like Galactus is to seriously cheapen Galactus' might and abilities. He's one of the major players in the Marvel multiverse, and one of the characters to arrive on the scene when there's a major threat to all of existence. To say that Thor is on the same plane as Galactus is just pure fantasy. I'm pro-Thor all the way, but let's keep him in his place. He's the premier hero on Earth, but that's about as far as it goes. And he's the strongest of the regular Marvel characters - except for the Hulk, of course, who's in a strength league all by his lonesome because of his the-madder-he-gets-the-stronger-he-gets magic potion that makes him eventually defeat any and all opponents, no matter how powerful, and which also has writers give him ridiculous powers, like pushing apart tectonic plates and jumping to the moon.
Strange, but I remember the Hulk being about 7 ft. tall back in the day when he was no stronger than Thor. Now, he's what? 15 ft. tall? What happened there? If the editors keep growing him stronger and stronger, he'll be the size of Giant-man. Or let's just make him Galactus-sized at 50 ft. tall and then take
him on. By that time Galactus' abilities like time-warping, thought-control, telekinesis, power blasts, etc, etc, will all be overcome by the Hulk's almighty cosmic punches. After all, the Hulk is the strongest one there is, right?
Maybe Marvel should do another Secret Wars/Infinity Gauntlet series where the Hulk gets so strong and becomes such a threat that all the cosmic deities have to get together again to team-up and defeat him. The Living Tribunal, Eternity, Galactus, Chaos and Order, the Stranger, Chronos, the Celestials, Thanos, Death, the Molecule Man, even the Beyonder (for good measure - have I missed anyone here?), etc, all fight to "take back" control from the uncontrollable Hulk. He defeats them all in the end, of course, with his unstoppable pounding fists. But all of existence is saved from the Hulk's pummeling at the last moment by The-One-Above-All, who it turns out was subtly manipulating the outcome the whole time.
Whew!
He gave Thor all kinds of weird, one-issue-only powers back in the '60s, too--much like the Superman comics of that period, in fact. Also, Thor used to strap Mjolnir to a lot of things and send them flying off to wherever he needed them to go. He actually duct-taped 3 crooks to a gurney, tied Mjolnir to the front, and threw them over to a police station in a Journey Into Mystery issue I read last night. 
